Printer Recirculation Control

ABSTRACT

Certain examples relate to controlling recirculation processes in a printing apparatus. An example printing material cartridge includes a reservoir storing printing material to supply a printing apparatus; memory; and instructions for controlling a recirculation process in the printing apparatus, the instructions stored in the memory, the recirculation process to cause the printing material to move between the reservoir and a second printing material cartridge, the second printing material cartridge separately replaceable from the printing material cartridge in the printing apparatus.

RELATED APPLICATIONS

This patent is a continuation of U.S. patent application Ser. No.16/959,044, filed on Jun. 29, 2020, and entitled “PRINTER RECIRCULATIONCONTROL.” U.S. patent application Ser. No. 16/959,044 arises from theU.S. national stage of International Patent Application No.PCT/US19/52224, filed on Sep. 20, 2019, and entitled “PRINTERRECIRCULATION CONTROL.” U.S. patent application Ser. No. 16/959,044 andInternational Patent Application No. PCT/US19/52224 are herebyincorporated by reference in their entireties. Priority to U.S. patentapplication Ser. No. 16/959,044 and International Patent Application No.PCT/US19/52224 is hereby claimed.

BACKGROUND

Most types of printing apparatus are equipped with replaceable printingmaterial cartridges that hold printing material for the printingprocess. Such printing material cartridges may include toner cartridgesthat contain laser printer toner, ink cartridges that contain differenttypes of ink, ribbon cartridges that include inked ribbons, and 3D buildmaterial cartridges that contain build material for 3D printers. Ink andother fluid containing cartridges may include materials that requireregular recirculation or mixing of the ink in order to avoidprecipitating heavy particles which may block the printing apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features of the present disclosure will be apparent from thedetailed description which follows, taken in conjunction with theaccompanying drawings, which together illustrate features of the presentdisclosure, and wherein:

FIG. 1 is a schematic illustration of a printing apparatus and supplyand mixing cartridges according to an example;

FIG. 2 is a schematic illustration of a supply cartridge according to anexample;

FIG. 3 is a schematic illustration of a mixing cartridge according to anexample;

FIG. 4 is a flow chart showing a method of operating a printingapparatus according to an example;

FIG. 5 is a user interface display according to an example;

FIG. 6 is a flow chart showing a method of operating a printingapparatus according to another example;

FIGS. 7A-7D are schematic illustrations of a printing apparatus andsupply and mixing cartridges according to another example at differentstages of a circulation process; and

FIG. 8 is a method of operating a printing apparatus according toanother example.

DETAILED DESCRIPTION

Printing material cartridges, such as those used for an ink jet printingapparatus, may contain a printing fluid which may be applied to a printmedium by the printing apparatus. The term “printing fluid” includes allfluids that may be deposited on a print medium from a cartridge andincludes fluids such as ink, toner, varnish, gloss, etc. Printingmaterial cartridges may also contain other material for use in printingprocesses including build material, heat absorbing or reducing agents,and colorants for 3D printing. For ease of explanation, an example ofink is used in the description herein; however, this should not be seenas limiting. An ink may be oil or water based with one or morecolorants, e.g. inks may be supplied as cyan, magenta, yellow and/orblack inks.

A printing material cartridge may comprise a reservoir or printing inkcontainer for storing the ink, as well as an integrated circuit havingmemory and a processor to perform identification, authentication, andother processes such as retrieving parameters related to the ink whichmay be used by the printing apparatus. The integrated circuit orsmart-chip is protected using memory encryption and limited logicoperations of the processor to ensure that the cartridge may only beused with the printing apparatus in an approved predetermined manner.For example, the printing apparatus may only use the cartridge when itcontains a predetermined memory setting that is not configurable by anexternal process, such as a code that may be verified by the printingapparatus. An example mechanism for secure interaction between theintegrated circuit of the cartridge and the printing apparatus isdescribed in PCT published patent document WO2016/068990.

The printing apparatus may retrieve information about the ink suppliedby the cartridge to ensure the cartridge has been installed correctly,is supported by the printing apparatus, or allows the printing apparatusto utilize appropriate color mapping or other processes dependent oncharacteristics of the ink such as color and chemical composition. Thecartridge also comprises an interface containing electrical and fluidconnections for interfacing with the printing apparatus. The cartridgeis removable from the printing apparatus such as an inkjet printer, sothat once the supply of ink is depleted, the cartridge may be replacedwith a new cartridge having a full supply of ink.

Certain types of ink may contain heavy particles such as titaniumdioxide (TiO₂) in white ink. Over time these particles may precipitateout of the liquid ink and fall to the lowest level of their container,conduit or local volume. These particles may cause blockages or otherissues such as reduced quality image reproduction by the printingapparatus and therefore the printing apparatus may implementrecirculation processes to regularly move the ink from one part of theprinting apparatus to another in order to avoid precipitation so thatthe particles remain fully dissolved in the ink. Different types of inkcontaining different particles or different concentrations of the sameparticles may require different recirculation processes. Recirculationmay also be used to address issues such as ink surface oxidation.Oxidation of ink at the surface is reduced by changing the ink at thesurface using recirculation and thus reducing the air exposure durationof any given volume of ink. Recirculation may also be used to addressother issues.

Using the incorrect recirculation process for an ink may result in poorimage reproduction by the printing apparatus due to some precipitationof heavy particles, and may result in blockage due to insufficientmixing of the ink. The recirculation process appropriate for the inkcontained in the cartridge may be preinstalled in the printing apparatusmemory or added later using a firmware update, or the process may bedownloaded manually by a user of the printing apparatus. However, it isnot always possible to ensure that the correct recirculation process isused as this may depend on a user correctly identifying the ink in thecartridge or the process being available in the memory of the printingapparatus.

Some cartridges containing inks requiring recirculation may be providedwith both a supply reservoir and a mixing reservoir which allows theprinting apparatus to move the ink between the reservoirs on a regularbasis in order to avoid precipitation of heavy particles. However, whenthe ink supply is depleted and the cartridge is replaced, both thesupply reservoir and the mixing reservoir must be replaced as thecartridge is provided as a unitary product. Typically, the ink supplymust be replenished more regularly than the mixing reservoir needs to bereplaced as the mixing reservoir may only be replaced at the end of itslife whereas the supply reservoir may be replaced upon depletion of inksupply. Therefore, replacing such cartridges is relatively expensive andenvironmentally unfriendly.

FIG. 1 illustrates a printing apparatus 100 including two removablecartridges 110 and 120. The printing apparatus comprises one or moreprint heads 130, one or more transport components such as pumps 145 andvalves 140, one or more pressure sensors 150 and pipes or ink conduits135 connecting the various parts. The printing apparatus may in someexamples also comprise an intermediate ink storage tank 147. Theprinting apparatus also comprises a controller 155 for controlling thevarious parts of the apparatus and includes a processor 157 and memory158. A user interface 160 provides printing apparatus status informationto a user and may allow a user to control some functions. The userinterface may include a display and input controls, for example a keypador a touchscreen. The printhead 130 deposits ink drops onto a printmedium and may be controlled to move across the print medium and deposita controlled number of drops of ink at predetermined locations in orderto preproduce an image.

The cartridges 110, 120 removably couple to a coupling interface 160which provides fluid communication with other parts of the printingapparatus 100 as well as electrical connection with the controller 155.Each cartridge 110, 120 comprises an ink reservoir 115, 125 and anintegrated circuit or smart-chip 112, 122 including protected memory.One of the cartridges is a supply cartridge 110 which is initiallyprovided with a full reservoir 115 containing ink for use in printing bythe printing apparatus and may be replaced when more ink is required.The other cartridge is a mixing cartridge 120 and is initially providedwith an empty reservoir 125 and is independently replaceable of thesupply cartridge 110, for example after a predetermined number of uses.The mixing cartridge 120 is used as a reservoir to facilitate inkrecirculation in which ink is regularly moved around the printingapparatus to ensure the ink is mixed often enough in order to avoidprecipitation of heavy particles. The controller 155 controls the pumps145 and valves 140 in order to move the ink from the supply cartridgereservoir 115 to the mixing cartridge reservoir 125, the intermediatetank 147, and/or the printhead 130. This movement of ink is typicallyperformed in repeated cycles known as recirculation events, where themovements are dependent on the ink. For example, some inks may needmixing more frequently than others.

The cartridge integrated circuits 112, 122 may be used to store datarelated to the ink, for example an identifier that can be used todetermine an appropriate recirculation process, an authentication codefor ensuring that only approved cartridges may be used with the printingapparatus, characteristics or other data related to the ink in orderassist with accurate color reproduction by the printing apparatus.Integrated circuits 112 and 122 for a supply cartridge 110 and a mixingcartridge 120 and according to an example are shown in more detail inFIGS. 2 and 3 respectively.

The integrated circuit 112 for the supply cartridge 110 includes aprocessor 213, memory 217 and an interface 215 for connecting with theelectrical part of the coupling interface 160. The processor 213 may beconfigured to provide limited functionality or may be instructed by thecontroller 155 of the printing apparatus, for example as an I2C slave.The memory 217 may contain protected fields that are not re-writable, ormay only be writable in a limited way for example as a counter onlywritable in one direction (increasing or decreasing). Some of the fieldsmay also be encrypted so that they can only be read with the correct keyto ensure that some information is only available to approved printingapparatus. In an example the memory 217 includes a supply cartridgeidentifier 230, a printing material counter 232, a reservoir printingmaterial level parameter 234, a removal protection parameter 236, apaired mixing cartridge identifier 250, recirculation processinstructions 255, a printing material characteristics parameter 240, andsecret key and authentication instructions for processor 242. Many ofthese data fields will be encrypted and otherwise protected to ensuretheir integrity.

The supply cartridge identifier 230 is a read only field containing aunique identifier for the cartridge. This may be used with the pairedmixing cartridge identifier 250 to pair a supply cartridge and a mixingcartridge so that once paired they may only be used together. When thesupply cartridge 110 is first used with the printing apparatus, theprinting apparatus reads a mixing cartridge identifier from an installedmixing cartridge and writes this to the paired mixing cartridgeidentifier field 250 of the supply cartridge memory 217. The printingapparatus may be configured to only use the supply cartridge 110 whenthis field 250 matches a mixing cartridge identifier stored on thepaired mixing cartridge 120. The supply cartridge identifier 230 mayalso be written to a corresponding paired supply cartridge identifierfield 350 on the mixing cartridge as described in more detail below.This ensures that the supply and mixing cartridges are paired to eachother to ensure correct operation of the system including for exampleavoiding mixing of incompatible inks. The printing apparatus may ensurethat ink characteristics data stored on each cartridge are compatible,for example that only supply cartridges having the same ink aspreviously used in the mixing cartridge are paired. By ensuring that thesupply cartridge and mixing cartridge only work together, printingsystem coherence is maintained. For example, only supply and mixingcartridges using the same ink are used together, the levels of thesystem ink and the ink in each reservoir 115, 125 are properlymaintained and the use of counterfeit cartridges is avoided. Were adifferent supply cartridge to be installed with a different ink to thatpreviously mixed in the mixing cartridge, the integrity of the colorrendered by the ink would be reduced and mixing of these different inksmay lead to other issues such as precipitation of heaving particles andblockage of the printing apparatus. This use of paired identifiers alsohelps to defeat the use of counterfeit cartridges which do not providefor storing of paired identifiers.

The printing material counter 232 is a non-resettable one-directionalcounter which is re-writable only to decrease (or increase) its valueand is indicative of the total level or amount of ink in the printingapparatus 100, including the supply cartridge 110 and the mixingcartridge 120. This total system ink counter is initially at a maximumwhen the supply cartridge is first installed and reduces as the ink isused for printing. The counter may be updated by the printing apparatus,for example when monitoring the number of drops of ink used in a printjob. The counter is not changed when the ink is moved as part of arecirculation process, for example from the supply cartridge to themixing cartridge, but only when the ink is consumed by printing so thatthe total or system ink is reduced.

The reservoir printing material level parameter 234 is indicative of theamount of printing material in the reservoir 115 and is a rewritablefield that may be updated by the printing apparatus, based for exampleon sensors in the reservoir, flowmeters in the printing apparatus, orestimated based on recirculation events. The level of ink in thereservoir 115 may go up as well as down, for example when ink istransferred from the mixing cartridge back to the supply cartridge aspart of a recirculation process.

The removal protection parameter 236 may be a resettable bit that isused to indicate whether the supply cartridge 110 may be removed fromthe printing apparatus 100. It may also be used to indicate whether thesupply cartridge can be accepted upon installation. The removalprotection parameter or bit may be set when not all of the ink in theprinting apparatus is stored in the supply cartridge reservoir 115. Inother words, there is still ink in the mixing cartridge 120. The removalprotection bit may be unset when all system ink is contained in thesupply cartridge. Whether or not the supply cartridge is removable maybe indicated by the user interface 160, and a user interface control mayallow a user to instruct the printing apparatus to move all ink to thesupply cartridge so that it may be replaced.

By ensuring that all of the ink is returned to the supply cartridgebefore removal and replacement with a new supply cartridge, the maximumlevel of ink in the printing apparatus is not exceeded. For example ifink is retained in the mixing cartridge and a new supply cartridge isinstalled, the total system level of ink may be too great to allow forrecirculation, thereby resulting in precipitation of particles and otherissues such as inaccurate monitoring of total system ink levels leadingto inaccurate indications of cartridge replacement requirements forexample. If the supply cartridge 110 is removed anyway, even with theremoval protection parameter indicating that it should not be, this bitwill remain set so that the supply cartridge will not be accepted byanother printing apparatus. The printing apparatus from which the supplycartridge was removed may need to perform some additional process beforeaccepting any new supply cartridges, for example the mixing cartridgemay need to be replaced with an empty one in order to ensure that themaximum level of ink in the printing apparatus is that provided with anew supply cartridge.

The printing material characteristics parameter 240 may containinformation about the ink in the reservoir 115, for example it's color,chemical composition such as pigments used and their concentrationcompared with a carrier, the use and amount or concentration ofdispersants, the use and amount or concentration of agents such astitanium dioxide, the use and amount or concentration of latex binders.Other information may include ink type or identifier, volume,manufacturing batch and other information. The field 242 containingsecret key and authentication instructions for processor 213 is used bythe processor to access the protected memory 217. The memory 217 alsocomprises recirculation process instructions 255 which may be used bythe printing apparatus to perform recirculation processes relevant tothe ink provided in the reservoir 115.

The integrated circuit 122 for the mixing cartridge 110 includes aprocessor 313, memory 317 and an interface 315 for connecting with theelectrical part of the coupling interface 160. The processor 313 may beconfigured to provide limited functionality or may be instructed by thecontroller 155 of the printing apparatus, for example as an I2C slave.The memory 317 may contain protected fields that are not re-writable, ormay only be writable in a limited way for example as a counter onlywritable in one direction (increasing or decreasing). Some of the fieldsmay also be encrypted so that they can only be read with the correct keyto ensure that some information is only available to approved printingapparatus. In an example the memory 317 includes a mixing cartridgeidentifier 330, a reservoir printing material level parameter 334, aremoval protection parameter 336, a paired mixing cartridge identifier350, a recirculation cycle counter 335, a maximum recirculation cycleparameter 337, a printing material characteristics parameter 340, andsecret key and authentication instructions for processor 342. Many ofthese data fields will be encrypted and otherwise protected to ensuretheir integrity

The mixing cartridge identifier 330 is a read only field containing aunique identifier for the cartridge. This may be used with the pairedsupply cartridge identifier 350 to pair a supply cartridge and a mixingcartridge so that once paired they may only be used together. When themixing cartridge 120 is first used with the printing apparatus, theprinting apparatus reads the mixing cartridge identifier 330 and writesthis to the paired mixing cartridge identifier field 250 of the supplycartridge memory. Similarly, the printing apparatus reads a supplycartridge identifier from an installed supply cartridge and writes thisto the paired supply cartridge identifier field 350 of the mixingcartridge memory 317. The printing apparatus may be configured to onlyuse the mixing cartridge 120 when this field 350 matches a supplycartridge identifier stored on the paired supply cartridge 120. Theprinting apparatus may ensure that ink characteristics data stored oneach cartridge are compatible, for example that only supply cartridgeshaving the same ink as previously used in the mixing cartridge arepaired. By ensuring that the supply cartridge and mixing cartridge onlywork together, printing system coherence is maintained. For example,only supply and mixing cartridges using the same ink are used together,the levels of the system ink and the ink in each reservoir 115, 125 areproperly maintained and the use of counterfeit cartridges is avoided.Once a supply cartridge is depleted, the paired supply cartridgeidentifier may be erased so that a new supply cartridge can beinstalled, and its identifier written to the paired supply cartridgeidentifier field 350 so that the mixing cartridge and the new supplycartridge are now paired. In another example, the pairing of the supplyand mixing cartridges may only occur when a recirculation process isongoing and the supply and/or mixing cartridges may be removed andinstalled in other printing apparatus when the ink is fully contained inthe supply cartridge.

The recirculation cycle counter 335 may be a non-resettableone-directional counter or field that stores the number of recirculationcycles or events experienced by the mixing cartridge 120. The counter335 may be updated by the printing apparatus as recirculation cycles areperformed, for example one cycle of moving the ink from the supplycartridge to the mixing cartridge and back to the supply cartridge. Themaximum recirculation cycle parameter 337 is a read-only field thatstores the maximum number of recirculation events that define theuseable lifetime of the mixing cartridge 120. The value of thisparameter may be dependent on the materials used to construct the mixingcartridge. When the value of the recirculation cycle counter 335 equals(or is greater than) the value of the maximum recirculation cycleparameter 337, the mixing cartridge is deemed unusable and can bereplaced.

The reservoir printing material level parameter 334 for the mixingcartridge 120 is indicative of the amount of printing material in thereservoir 125 and is a rewritable field that may be updated by theprinting apparatus, based for example on sensors in the reservoir,flowmeters in the printing apparatus, or estimated based onrecirculation events. The level of ink in the reservoir 125 will varydepending on recirculation processes as ink is transferred to and fromthe mixing cartridge 120.

A removal protection parameter 336 may also be used in the mixingcartridge. The removal protection parameter may be a resettable bit thatis used to indicate whether the mixing cartridge 110 may be removed fromthe printing apparatus 100. It may also be used to indicate whether themixing cartridge can be accepted upon installation. The removalprotection parameter or bit may be set when there is ink in the mixingcartridge reservoir 125. The removal protection bit 334 for the mixingcartridge may be unset when there is no ink in the mixing cartridge.Whether or not the supply cartridge is removable may be indicated by theuser interface 160, and a user interface control may allow a user toinstruct the printing apparatus to move all ink to the supply cartridgeso that the mixing cartridge may be replaced.

The printing apparatus 100 may also store the cartridges identifiers 230and 330 in memory 158 when setting the corresponding removal protectionparameter 236 and 336 in the supply and mixing cartridge memories 217and 317. This may allow the printing apparatus 100 to accept cartridgeshaving their removal protection parameter 236 or 336 set when theircartridge identifier 230 or 330 matches that stored in the printingapparatus memory 158. This arrangement allows a cartridge 110 and/or 120to be tied to a single printing apparatus 100 using the removalprotection bit 236 or 336 stored on the cartridge memory 217, 317 andthe cartridge identifier 230, 330 stored on the printer apparatus memory158. For example even if the cartridge is removed with the removalprotection bit set, the printing apparatus may be configured to acceptit if its cartridge identifier 230, 330 is stored on the printingapparatus memory 158.

The printing material characteristics parameter 340 may containinformation about the ink that the reservoir 125 may accept, for exampleit's color, chemical composition, type or identifier, volume,manufacturing batch and other information. The field 342 containingsecret key and authentication instructions for processor 313 is used bythe processor to access the protected memory 317.

FIG. 4 illustrates a method 400 of operating a printing apparatus andmay be implemented by the controller 155 of the printing apparatus ofFIG. 1 and the integrated circuits and fields in the supply and mixingcartridges 110, 120 of FIGS. 2 and 3. The method 400 may be performed tocontrol recirculation of certain inks as well as to control use ofseparately removable supply and mixing cartridges. At block 405, themethod 400 comprises retrieving data from the supply and mixingcartridges. The data may include ink characteristics parameters 240,340, removal protection parameters 236, 336, cartridge identifiers 230,330 and paired cartridge identifiers 250, 350, system ink counter 232,reservoir levels 234, 334, recirculation cycles counter 335 and maximumrecirculation cycles 337.

At block 410, the method 400 determines whether this data allowsoperation of the printing apparatus to proceed. For example if thecartridge identifiers 230, 330 are not legitimate, if the removalprotection bits 236, 336 are set, the paired cartridge identifier fields250, 350 do not match the corresponding cartridge identifier fields 330,230, or the recirculation cycle counter value 335 is not less than thevalue in the maximum recirculation cycles field 337, then the cartridgesmay be rejected by the printing apparatus 100. In this case the method400 may move to block 415 where an error message is displayed to a useron the user interface 160. A more detailed explanation of use of thepaired cartridge identifiers 250, 350 is described in more detail belowwith respect to FIG. 8. If the data from the cartridges 110, 120 isdetermined to allow operation of the cartridges with the printingapparatus, the method moves to block 420. Otherwise the method moves toan error state 415 which may result in a user notification.

At block 420, the method 400 operates the printing apparatus 100 bycontrolling pumps 145 and values 140 to move ink between different partsof the printing apparatus. For example ink may be moved from the supplycartridge reservoir 115 to the intermediate tank 147 and/or to themixing cartridge reservoir 125 in order to mix the ink to avoidprecipitation of heaving particles. The ink may then be moved back tothe supply cartridge reservoir 115 in order to complete a recirculationcycle. The ink may also be moved from the supply cartridge or the mixingcartridge to the printhead to enable printing of an image onto aprinting medium.

At block 425, after each ink moving operation, the method updates thedata fields in the cartridges 110, 120. For example, the reservoirprinting material level parameters 234, 334 are updated as ink movesinto and out of these storage volumes. Similarly, the printing materialcounter 232 is updated as the printhead expels ink, thereby reducing thetotal ink in the system. The removal protection parameter(s) 236, 336are set when not all of the system ink is contained in the supplycartridge reservoir 115. This may be implemented by comparing theprinting material counter 232 with the reservoir printing material levelparameter 234 of the supply cartridge—if the former is larger than thelater this indicates that some of the total system ink is contained inother parts of the printing apparatus, for example in the mixingcartridge. If the ink movement completes a recirculation cycle (e.g.moving ink back to the supply cartridge), the recirculation cyclecounter 335 in the mixing cartridge is updated.

At block 430, the method 400 determines whether the system ink is low,for example by checking if the value of the printing material counter232 is below a threshold. If this is not the case, the method moves toblock 435 and determines whether the recirculation cycle counter 335 hasreached its maximum threshold, the value stored in the maximumrecirculation cycles field 337. If this is not the case, the methodreturns to the next printing apparatus operation at block 420.

If the total or system ink is low, the method moves to block 440 wherethe ink in the printing apparatus is moved to the supply cartridgereservoir 115. At block 445, the removal protection parameter 236 isunset which indicates that the supply cartridge may be replaced by auser at block 450. The method then returns to block 405. If therecirculation cycle counter 335 has reached its maximum threshold, themethod 400 again moves to block 440 to ensure that any ink in theprinting apparatus is moved to the supply cartridge 110. If a removalprotection parameter 336 is used in the mixing cartridge 120, this maybe unset at block 445 which indicates that the mixing cartridge may bereplaced by a user at block 450. The method then returns to block 405.

Referring to FIG. 5, a display for the user interface 160 is shown. Thisincludes a window 510 for a supply cartridge 110 and a window 520 for amixing cartridge 120. The supply cartridge window includes an icon 512indicating the total ink within the printing apparatus—in this caseindicating that the total ink is at approximately 75% capacity. Thisicon corresponds to the printing material counter 232. A second icon 514indicates the level of ink within the supply cartridge reservoir 115—inthis case approximately half full and not all system ink is contained inthe reservoir 115. This icon corresponds to the reservoir printingmaterial level parameter 234 of the supply cartridge. A third icon 516indicates whether the supply cartridge 110 can be removed, for exampleto replace with a new supply cartridge with full reservoir 115. Thisicon corresponds with the removal protection parameter 236 of the supplycartridge and may include a “don't remove” warning indicator when notall of the system ink is contained in the supply cartridge as is thesituation shown. The mixing cartridge window 520 includes an icon 524indicating the level of ink within the mixing cartridge reservoir 125—inthis case approximately one quarter full. This icon corresponds to thereservoir printing material level parameter 334 of the mixing cartridge.Another icon 526 indicates whether the mixing cartridge 110 can beremoved, for example to replace with a new mixing cartridge. This iconcorresponds with the removal protection parameter 336 of the mixingcartridge (if used) and may include a “don't remove” warning indicatorwhen not all of the system ink is contained in the supply cartridge (orwhen there is some ink in the mixing cartridge reservoir 125) as in thesituation shown.

FIG. 8 illustrates a method 800 of operating a printing apparatus andmay be implemented by the controller 155 of the printing apparatus ofFIG. 1 and the integrated circuits and fields in the supply and printingcartridges 110, 120 of FIGS. 2 and 3. The method 800 may be performed topair a supply cartridge with a particular mixing cartridge in order toprevent improper operation of the printing apparatus should one of thecartridges be replaced with a different type or a counterfeit cartridgewhich may not include some or all of the previously described fieldsused to enable the above described operation. Inaccurate or missingfields may result in incorrect operation of the printer, poor qualityprinting and possible damage. For example, as described above theprinting apparatus tracks the total ink in the system as well as levelsof ink in each of the reservoirs 115, 125 by updating data 232, 234, 334securely stored in the memory 217, 317 of the cartridges 110, 120. If adifferent cartridge is incorrectly installed, the total ink level may beincorrect leading to poor operation of the printing apparatus andpossibly damage.

At block 805 the method 800 retrieves cartridge identifiers 230, 330from the supply and mixing cartridges 110, 120 and if available thepaired cartridge identifiers 250, 350. At block 810 the method 800determines if the paired cartridge identifiers 250, 350 from eithercartridge are empty. This may occur if the cartridge 110 or 120 has beennewly installed. In this case, the method moves to block 820 where thecartridge identifier 230 or 330 is written to the paired cartridgeidentifier field 350 or 250 of the other cartridge. For example, thecartridge identifier 230 of the supply cartridge 110 is written into thepaired cartridge identifier 350 of the mixing cartridge 120. Similarly,the cartridge identifier 330 of the mixing cartridge 120 is written intothe paired cartridge identifier 250 of the supply cartridge 120. Checksto ensure that the cartridges are not counterfeit may be performedinitially, for example that an authentication process can be performedby each cartridge. If there are no fields for paired cartridgeidentifiers this may also indicate a counterfeit cartridge. In thesecases an error message may be displayed to a user of the printingapparatus that the cartridge(s) can not be accepted.

If the paired cartridge identifiers 250, 350 are recovered, the method800 moves to block 830 where these are checked against the cartridgeidentifier 230, 330 in the other cartridge. For example, the pairedcartridge identifier 250 in the supply cartridge 110 is compared withthe cartridge identifier 330 in mixing cartridge 120. If these do notmatch the method moves to block 835 where an error message is displayedto a user and the cartridge is rejected for use with the printingapparatus. Similarly, the paired cartridge identifier 350 in the mixingcartridge 120 is compared with the cartridge identifier 230 in supplycartridge 110. If these do not match the method moves to block 835 wherean error message is displayed to a user and the cartridge is rejectedfor use with the printing apparatus. If the paired cartridge identifiers250, 350 do match the cartridge identifiers 330, 230 on the othercartridge, then the method moves to block 825 where operation of theprinting apparatus using the cartridges may begin—for example asdescribed above.

The method 800 ties a supply and mixing cartridges together so that theycan only be used together in a printing apparatus 100. The pairedcartridge identifiers 250, 350 may be used with or without the removalprotection parameters 236, 336 which can be used to tie a cartridge 110,120 to a particular printing apparatus 100. For example, using only thepaired cartridge identifiers 250, 350 it is possible that thecorresponding cartridges 110, 120 may be used together in a differentprinting apparatus.

Referring to FIG. 6, a method 600 of operating a printing apparatus isillustrated and may be implemented by the controller 155 of the printingapparatus of FIG. 1 and the integrated circuits and fields in the supplycartridges 110 of FIG. 2. The method 600 may be performed to controlrecirculation processes within the printing apparatus 100 using processinstructions stored on the supply cartridge 110. The recirculationprocess may be specific to ink stored in the reservoir 115 and/or to theprinting apparatus 100 on which the recirculation is to be performed. Asnoted above, the process instructions may be stored in a field orlocation 255 of the integrated circuit memory 217. The processinstructions may be stored in the form of an encrypted, compressed XMLfile, although other file types may alternatively be used. More than oneset of process instructions may be stored for use with differentprinting apparatus.

At block 605, the printing apparatus checks the supply cartridge for arecirculation process file. Where multiple sets of process instructionsare included for different printing apparatus, an index may be providedincluding printing apparatus identifiers to indicate whether theprinting apparatus is supported. At block 610, if no process file orinstructions are found, the method moves to block 630 to reject thecartridge and to indicate an error message to the user. If appropriateprocess instructions 255 are found, the method moves to block 620.

At block 620 the process instructions 255 are retrieved from thecartridge 110 and are decompressed. The decompressed processinstructions may be in the form of an XML file containing instructionsdirectly interpretable by the controller 155 of the printing apparatus100. At block 625 the controller executes the instructions to transportink to and from the cartridge 110 as well as within the printingapparatus in order to mix the ink to avoid precipitating particles whichmay cause blockages and/or reduce print quality.

An example of process instructions is shown below and is described withrespect to FIGS. 7A and 7B. The printing apparatus 700 comprises pumps745 (labelled P-1 and P-2 in the figure and pump_1 and pump_2 in the XMLcode below) and valves 740 (labelled V-1, V-2, V-3, V-4 in the figureand valve_1, valve_2, valve_3, valve_4 in the XML code below). Thesetransport components are controlled to move ink within the printingapparatus to its different parts, including to and from the supplycartridge 710 and a mixing cartridge 720. The heavy lines show transportof the ink, in the case of FIG. 7A from the supply cartridge 710 to themixing cartridge 720, and in the case of FIG. 7B the reserve directionfrom the mixing cartridge back to the supply cartridge. Thisrecirculation cycle may be repeated at predetermined time periods,following periods of inactivity where no printing occurs, or followingor preceding other recirculation cycles. This or a combination ofrecirculation cycles may depend on the ink being transported and/or theprinting apparatus used.

An XML file for the operations illustrated in FIGS. 7A and 7B is shownbelow:

<processing>  <xml xml_index=“1” version=“1” encoding=“utf-8”/> <mixing_AtoB>  <pump_1 action=“ON” duration=“10” PWM= “50” direction=“reverse”/>  <pump_1 action=“ON” duration=“10” PWM= “50” direction=“reverse”/>  <pump_2 action=“OFF” duration=“10” PWM= “0” direction=“forward”/>   <valve_1 action=“power_off” duration=“20”/>  <valve_2 action=“power_off” duration=“20”/>   <valve_3action=“power_on” duration=“20”/>   <valve_4 action=“power_on”duration=“20”/>   <trigger stop=“time”/>  </mixing_AtoB>  <mixing_BtoA> <pump_1 action=“ON” duration=“10” PWM= “50”  direction=“reverse”/> <pump_2 action=“OFF” duration=“10” PWM= “0”  direction=“forward”/>  <valve_1 action=“power_on” duration=“20”/>   <valve_2action=“power_on” duration=“20”/>   <valve_3 action=“power_off”duration=“20”/>   <valve_4 action=“power_off” duration=“20”/>   <triggerstop=“time”/>  </mixing_BtoA> </processing>

In order to move the ink from the supply cartridge 110 to the mixingcartridge 120, pump_1 (V-1) is turned on in the reverse direction andpump_2 (P-2) is off, valve_1 (V-1) and valve_2 (V-2) are closed andvalve_3 (V-3) and valve_4 (V-4) are open. In order to move the ink backfrom the mixing cartridge 120 to the supply cartridge 110, pump_1 (V-1)is turned on in the reverse direction and pump_2(P-2) is off, valve_1(V-1) and valve_2 (V-2) are open and valve_3 (V-3) and valve_4 (V-4) areclosed. The process description or instructions are shown for printerxml_index=1; different printers may use the same or different processinstructions.

Process instructions for a different ink are shown below and aredescribed with respect to FIGS. 7C and 7D. The instructions are for thesame printing apparatus, or same group of printing apparatus, andrequires more complex recirculation than the first ink type, includingpassing through the printhead 730.

In order to move the ink from the supply cartridge 110 to the mixingcartridge 120, pump_1 (V-1) is turned off and pump_2 (P-2) is turned onin the forward direction. Valve_1 (V-1) and valve_2 (V-2) are closed andvalve_3 (V-3) and valve_4 (V-4) are open. In order to move the ink backfrom the mixing cartridge 120 to the supply cartridge 110, pump_1 (V-1)is turned off and pump_2 (P-2) is turned on in the forward direction.Valve_1 (V-1) and valve_2 (V-2) are open and valve_3 (V-3) and valve_4(V-4) are closed.

An XML file for the operations illustrated in FIGS. 7A and 7B is shownbelow:

<processing>  <xml xml_index=“3” version=“2” encoding=“utf-8”/> <mixing_AtoB>  <pump_1 action=“OFF” duration=“10” PWM= “50” direction=“reverse”/>  <pump_2 action=“ON” duration=“10” PWM= “25” direction=“forward”/>   <valve_1 action=“power_off” duration=“20”/>  <valve_2 action=“power_off” duration=“20”/>   <valve_3action=“power_on” duration=“20”/>   <valve_4 action=“power_on”duration=“20”/>   <trigger stop=“pressure” target=“10psi”/>  <pump_1action=“OFF” duration=“10” PWM= “0”  direction=“reverse”/>  <pump_2action=“OFF” duration=“10” PWM= “0”  direction=“forward”/>   <valve_1action=“power_off” duration=“0”/>   <valve_2 action=“power_off”duration=“0”/>   <valve_3 action=“power_off” duration=“0”/>   <valve_4action=“power_off” duration=“0”/>   <trigger stop=“time”/> </mixing_AtoB>  <mixing_BtoA>  <pump_1 action=“OFF” duration=“10” PWM=“50”  direction=“forward”/>  <pump_2 action=“ON” duration=“10” PWM= “25” direction=“reverse”/>   <valve_1 action=“power_on” duration=“20”/>  <valve_2 action=“power_on”duration=“20”/>   <valve_3action=“power_off” duration=“20”/>   <valve_4 action=“power_off”duration=“20”/>   <trigger stop=“pressure” target=“10psi”/>  <pump_1action=“OFF” duration=“10” PWM= “0”  direction=“reverse”/>  <pump_2action=“OFF” duration=“10” PWM= “0”  direction=“forward”/>   <valve_1action=“power_off” duration=“0”/>   <valve_2 action=“power_off”duration=“0”/>   <valve_3 action=“power_off” duration=“0”/>   <valve_4action=“power_off” duration=“0”/>  <trigger stop=“time”/> </mixing_BtoA> </processing>

A combination of these actions may be performed for predetermined timeperiods and the same or different pump rates. The same or different timeperiods may be used for controlling the valves. This file also has ahigher version number so the printing apparatus uses the latest versioneven if an earlier version is stored locally, for example from afirmware update, or an earlier cartridge stored process description orinstructions.

The controller 155 interprets the recirculation instructions and maycontrol various components such as pumps using local operating systeminstructions. Various compression algorithms may be used for compressingthe recirculation process instructions file, including for example thosedescribed in PCT patent publication WO2017/086989. Variousauthentication and control processes may be used to ensure that theprocess instructions 255 are protected in the integrated circuit orsmart chip and are only accessible by authorized printing apparatus. Forexample, the cartridge processor 213 may be an I2C slave microcontrollerand the printer controller processor 157 may be the I2C master. Themicrocontroller 213 may be read by the printer controller 155, 157 byaddressing a read field and cryptographically authenticating the readmessage and loading into a read field, although other secure methods maybe employed. An example of a mechanism for securely interacting with acartridge is described in PCT patent publication WO2016/068990.

In another example, a separate removable mixing cartridge may not beused and the ink may be moved between the supply cartridge, anintermediate tank permanently within the printing apparatus and theprinthead(s). In other examples a different file type may be used thanXML to contain recirculation instructions which can be retrieved by aprinting apparatus and executed. The recirculation process may betriggered in different ways, for example based on time, temperature,printer usage, ink levels, etc.

The process instructions may be adapted to the ink in the supplycartridge. For example, a whitening agent such as titanium dioxide TiO2particles may be dissolved in a carrier together with a dispersantadditive which keeps the particles in suspension longer, but this candecrease the performance of the ink in the printing process. The ratiobetween dispersant and TiO2 particles therefore needs to be carefullycontrolled and the recirculation processes can be tailored to ensureappropriate movement of the ink depending on different ink compositionsin order to avoid precipitation of the particles. Therefore, therecirculation instructions may be updated as ink compositions changeover time and the most appropriate recirculation procedures can beincorporated by printing apparatus when the supply cartridge isinstalled thereby effectively adapting older printers (as well as newprinters) to changing ink compositions over time.

In some examples the ink may comprise one or more of the following:white pigments; titanium dioxide; dye sub ink; reactive ink; enamel ink;organic compounds; latex binders. The printing material cartridge mayinclude an at least partially flexible container to hold the ink and asupport structure to hold the container. The container may be is a bagand the support structure may be a carton box. In some examples thecarton box may contain a single bag and in other examples the carton boxmay contain two or more bags.

In some examples, the percentage of solid pigments by weight isapproximately 20-25% for white inks and 10-15% for other inks. In otherexamples the solid pigments by weight is 15-30% for white ink and 10-20%for other inks. In some examples the D90 particle distribution for whiteinks is approximately 350-550 nm and 200-450 nm for other inks. In otherexamples the D90 particle size distribution for white inks is 300-600 nmand 150-500 nm for other inks.

The preceding description has been presented to illustrate and describeexamples of the principles described. This description is not intendedto be exhaustive or to limit these principles to any precise formdisclosed. Many modifications and variations are possible in light ofthe above teaching. It is to be understood that any feature described inrelation to any one example may be used alone, or in combination withother features described, and may also be used in combination with anyfeatures of any other of the examples, or any combination of any otherof the examples

What is claimed is:
 1. A printing material cartridge comprising: areservoir storing printing material to supply a printing apparatus;memory; and instructions for controlling a recirculation process in theprinting apparatus, the instructions stored in the memory, therecirculation process to cause the printing material to move between thereservoir and a second printing material cartridge, the second printingmaterial cartridge separately replaceable from the printing materialcartridge in the printing apparatus.
 2. The printing material cartridgeof claim 1, further including a removal protection parameter stored inthe memory, the removal protection parameter indicative of whether theprinting material cartridge is removable from the printing apparatus. 3.The printing material cartridge of claim 2, wherein the removalprotection parameter is indicative of a presence of at least a portionof the printing material at the second printing material cartridge. 4.The printing material cartridge of claim 1, further including a printingmaterial characteristics parameter stored in the memory, the printingmaterial characteristics parameter indicative of a characteristic of theprinting material.
 5. The printing material cartridge of claim 4,wherein the characteristic includes one or more of a pigment compositionof the printing material, a concentration of dispersants for theprinting material, a concentration of agents for the printing material,or a concentration of latex binders for the printing material.
 6. Theprinting material cartridge of claim 1, further including a firstcartridge identifier and a second cartridge identifier stored in thememory, the first cartridge identifier associated with the printingmaterial cartridge and the second cartridge identifier associated withthe second printing material cartridge.
 7. The printing materialcartridge of claim 6, wherein the second cartridge identifier isindicative of a pairing between the printing material cartridge and thesecond printing material cartridge.
 8. A printing material cartridgecomprising: a reservoir storing printing material to supply a printingapparatus; memory; and a printer material counter stored in the memory,the printer material counter indicative of a total amount of theprinting material in the reservoir and a second printing materialcartridge, the second printing material cartridge separately replaceablefrom the printing material cartridge in the printing apparatus.
 9. Theprinting material cartridge of claim 8, wherein the printer materialcounter has a first value, the printer material counter to maintain thefirst value when the printing material is moved between the reservoirand the second printing material cartridge.
 10. The printing materialcartridge of claim 9, wherein the first value of the printer materialcounter is to change in response to consumption of the printing materialat the printing apparatus.
 11. The printing material cartridge of claim8, further including a reservoir printing material level parameterstored in the memory, the reservoir printing material level parameterindicative of an amount of printing material in the reservoir.
 12. Theprinting material cartridge of claim 11, wherein a value of thereservoir printing material level parameter is to change in response to(a) consumption of the printing material at the printing apparatus and(b) movement of the printing material between the reservoir and thesecond printing material cartridge.
 13. The printing material cartridgeof claim 8, further including a removal protection parameter stored inthe memory, the removal protection parameter having (a) a first statuswhen the printing material is in the reservoir and not the secondprinting material cartridge and (b) a second status when a first portionof the printing material is in the reservoir and a second portion of theprinting material is at second material cartridge.
 14. The printingmaterial cartridge of claim 13, wherein the first status indicates thatthe printing material cartridge is removable from the printingapparatus.
 15. The printing material cartridge of claim 14, wherein theremoval protection parameter is to change from the second status to thefirst status in response to recirculation of the printing material atthe printing apparatus.